Living fishes The living fishes (not a monophyletic group) include: the jawless fishes (e.g. lampeys), the jawless fishes (e.g. lampeys), cartilaginous

Living fishesLiving fishes

The living fishes (not a monophyletic The living fishes (not a monophyletic group) include:group) include: the jawless fishes (e.g. lampeys), the jawless fishes (e.g. lampeys), cartilaginous fishes (e.g. sharks and rays), cartilaginous fishes (e.g. sharks and rays), bony, ray-finned fishes (most of the bony bony, ray-finned fishes (most of the bony

fishes such as trout, perch, pike, carp, etc) fishes such as trout, perch, pike, carp, etc) and and

the bony, lobe-finned fishes (e.g. lungfishes, the bony, lobe-finned fishes (e.g. lungfishes, coelacanth).coelacanth).

16.1

Figure 24.01

16.2

Figure 24.02

Bony fishes: OsteichthyesBony fishes: Osteichthyes

The term osteichthyes does not describe a The term osteichthyes does not describe a monophyletic group, but is a term of monophyletic group, but is a term of convenience to describe the fishes whose convenience to describe the fishes whose skeletons are made of bone that replaces skeletons are made of bone that replaces cartilage during embryonic development.cartilage during embryonic development.

There are two classes the Actinopterygii There are two classes the Actinopterygii (the ray-finned fishes) and the (the ray-finned fishes) and the Sarcopterygii (the lobe-finned fishes)Sarcopterygii (the lobe-finned fishes)

General characteristics of bony fishGeneral characteristics of bony fish

Skeleton made of bone of endochondral Skeleton made of bone of endochondral origin (derived from cartilage).origin (derived from cartilage).

Paired and median fins supported by Paired and median fins supported by dermal rays.dermal rays.

Respiration mainly by gills. Gills covered Respiration mainly by gills. Gills covered with operculum.with operculum.

Swim bladder often present.Swim bladder often present. Complex nervous, circulatory and Complex nervous, circulatory and

excretory systems presentexcretory systems present

Class Actinopterygii (ray-finned Class Actinopterygii (ray-finned fishes)fishes)

This is by far the larger of the two living This is by far the larger of the two living classes of fishes with more than 27,000 classes of fishes with more than 27,000 species.species.

Includes probably every fish you can think Includes probably every fish you can think of. E.g. salmon, cod, herring, tuna, marlin, of. E.g. salmon, cod, herring, tuna, marlin, pike, sardine, clownfish, goldfish.pike, sardine, clownfish, goldfish.

Divisions of ActinopterygiiDivisions of Actinopterygii

The Actinopterygii are divided into two groups The Actinopterygii are divided into two groups Palaeonisciformes (formerly known as the Palaeonisciformes (formerly known as the

“chondrosteans”), which includes the relic species just “chondrosteans”), which includes the relic species just mentioned.mentioned.

Neopterygii, which includes the most derived and Neopterygii, which includes the most derived and most recent group of ray-finned fishes the Teleostei most recent group of ray-finned fishes the Teleostei and a number of primitive species including the gars and a number of primitive species including the gars and bowfins. These primitive Neopterygii were once and bowfins. These primitive Neopterygii were once grouped as the “holosteans.”grouped as the “holosteans.”

Ancestral ray finned fishes in the Devonian Ancestral ray finned fishes in the Devonian were small and heavily armored with were small and heavily armored with ganoidganoid scales (thick, bony, non- scales (thick, bony, non-overlapping, relatively inflexible scales) overlapping, relatively inflexible scales) and heterocercal tails (shaped like that of and heterocercal tails (shaped like that of modern sharks).modern sharks).

Figure 24.18

Palaeonisciformes Palaeonisciformes “Chondrosteans”“Chondrosteans”

A few relic species still possess such A few relic species still possess such characteristics. characteristics.

These include sturgeon and paddlefish These include sturgeon and paddlefish which are included in the which are included in the Acipenseriformes and the bichirs Acipenseriformes and the bichirs (Polypteriformes).(Polypteriformes).

Figure 24.19

PalaeonisciformesPalaeonisciformes

The relatively few surviving The relatively few surviving Palaeonisciformes are the remnant of Palaeonisciformes are the remnant of what was once a much more diverse what was once a much more diverse group. group.

Palaeonisciformes were the first bony Palaeonisciformes were the first bony fishes and were most diverse in the fishes and were most diverse in the Carboniferous and Permian.Carboniferous and Permian.

PalaeonisciformesPalaeonisciformes

Extinct palaeoniscids were mostly small < Extinct palaeoniscids were mostly small < 0.5m with a fusiform shape which 0.5m with a fusiform shape which suggests they were active foragers.suggests they were active foragers.

They were covered with small diamond-They were covered with small diamond-shaped scales.shaped scales.

The base of each scale was made of The base of each scale was made of bone, the middle of dentin and the surface bone, the middle of dentin and the surface with an enamel-like substance called with an enamel-like substance called ganoine. Hence the name ganoine. Hence the name ganoidganoid scales. scales.

Sturgeons and PaddlefishSturgeons and Paddlefish

These lack ganoid scales except for in These lack ganoid scales except for in sturgeons the rows of enlarged scales that sturgeons the rows of enlarged scales that run along the sides of the body.run along the sides of the body.

The skeleton is almost entirely The skeleton is almost entirely cartilaginous, which has resulted from the cartilaginous, which has resulted from the loss of mineralization.loss of mineralization.

PaddlefishPaddlefish

The two species of Paddlefish are found in fresh The two species of Paddlefish are found in fresh water in North America and China. The Chinese water in North America and China. The Chinese species is nearly extinct.species is nearly extinct.

About 2m long paddlefish possess an elongated About 2m long paddlefish possess an elongated flattened rostrum, which is believed to be used flattened rostrum, which is believed to be used to detect tiny, electric fields. to detect tiny, electric fields.

The North American paddlefish is a planktivore.The North American paddlefish is a planktivore.

http://blocs.xtec.cat/englishcornersallaresipla/files/2008/01/paddlefish2.jpg

SturgeonsSturgeons

There are 24 species of sturgeons and all are There are 24 species of sturgeons and all are large fish that reach up to 6m in length.large fish that reach up to 6m in length.

They have a protrusible jaw (evolved They have a protrusible jaw (evolved independently of the teleosts) which they use for independently of the teleosts) which they use for suction feeding.suction feeding.

They are commercially important for their meat, They are commercially important for their meat, but especially their eggs (caviar).but especially their eggs (caviar).

http://www.fishingmagic.com/news/images/Canada_Record_Sturgeon_lg.jpg

http://fish.dnr.cornell.edu/nyfish/Acipenseridae/shortnose_sturgeon.jpg

http://cordonnoir.com/images/Caviar_fresh.jpg

BichirsBichirs There are 11 species of bichir and they are There are 11 species of bichir and they are

considered the most primitive surviving group of considered the most primitive surviving group of the ray-finned fishes.the ray-finned fishes.

They are heavily armored with dermal bone and They are heavily armored with dermal bone and a thick layer of ganoid scales.a thick layer of ganoid scales.

Occur in swamps and streams in Africa and Occur in swamps and streams in Africa and have a swim bladder that acts like a paired have a swim bladder that acts like a paired ventral lung. They will drown if unable to gulp air ventral lung. They will drown if unable to gulp air at the surface.at the surface.

Armored Bichirhttp://www.aquarticles.com/images/Gallo/Armoured%20bichir%202.gif

http://www.fbas.co.uk/Bichir.jpg

BichirsBichirs

Because bichirs have paired fleshy Because bichirs have paired fleshy pectoral fins and lungs they were formerly pectoral fins and lungs they were formerly classified with the lungfishes, but are now classified with the lungfishes, but are now considered to have evolved these traits considered to have evolved these traits independently.independently.

Neopterygii: “holosteans”Neopterygii: “holosteans” There are two genera of primitive Neopterygians There are two genera of primitive Neopterygians

that were previously grouped together as that were previously grouped together as holosteans.holosteans.

Both have more flexible jaws than Palaoniscids, Both have more flexible jaws than Palaoniscids, but less flexible than those of more advanced but less flexible than those of more advanced Neopterygians.Neopterygians.

These are the seven species of gars These are the seven species of gars (Lepisosteiformes) and the single species of (Lepisosteiformes) and the single species of bowfin (Amiiformes).bowfin (Amiiformes).

GarsGars

Gars are medium to large (1-4m) Gars are medium to large (1-4m) predatory fish with a distinctive elongated predatory fish with a distinctive elongated body and long jaws.body and long jaws.

They have hard, interlocking, multilayered They have hard, interlocking, multilayered ganoid scales which provide excellent ganoid scales which provide excellent protection and are similar to the scales of protection and are similar to the scales of many extinct Paleozoic and Mesozic many extinct Paleozoic and Mesozic actinoptrygians.actinoptrygians.

Longnose garhttp://www.biokids.umich.edu/files/12296/gar_large.jpg

http://animals.nationalgeographic.com/staticfiles/NGS/Shared/StaticFiles/animals/images/primary/gar.jpg

BowfinBowfin

There is only one species of bowfin.There is only one species of bowfin.

Its scales are of a single layer of bone as Its scales are of a single layer of bone as in teleosts, but the caudal fin is in teleosts, but the caudal fin is asymmetric and similar to that of more asymmetric and similar to that of more primitive fishes.primitive fishes.

Bowfinhttp://pond.dnr.cornell.edu/nyfish/Amiidae/bowfin.jpg

TeleostsTeleosts

The vast majority of modern fishes are The vast majority of modern fishes are ““teleosts.”teleosts.”

They have replaced the heavy armored They have replaced the heavy armored scales of their ancestors with much lighter scales of their ancestors with much lighter more flexible scales that overlap each more flexible scales that overlap each other and also have evolved homocercal other and also have evolved homocercal symmetrical tails.symmetrical tails.

Figure 24.15

Figure 24.18

Teleost charactersTeleost characters

Homocercal tailHomocercal tail Circular scales without ganoineCircular scales without ganoine Ossified vertebraeOssified vertebrae Swim bladderSwim bladder Skull with complex jaw mobilitySkull with complex jaw mobility

Teleost classificationTeleost classification

How the Neopterygii should be subdivided How the Neopterygii should be subdivided differs greatly from authority to authority.differs greatly from authority to authority.

We will use the text’s division of the We will use the text’s division of the teleosts into three large groups:teleosts into three large groups: TeleosteiTeleostei EuteleosteiEuteleostei AcanthopterygiiAcanthopterygii

Diversity of bony fishes: TeleosteiDiversity of bony fishes: Teleostei

There are three major clades of the TeleosteiThere are three major clades of the Teleostei

OsteoglossomorphaOsteoglossomorpha: [greek bony tongue]. About 220 : [greek bony tongue]. About 220 species of tropical freshwater fish. Includes from the species of tropical freshwater fish. Includes from the Amazon Amazon OsteoglossumOsteoglossum or Arawana, and Arapaima the or Arawana, and Arapaima the largest purely freshwater fish (regularly 3m long, but up largest purely freshwater fish (regularly 3m long, but up to 4.5 m).to 4.5 m).

Also includes the African elephant nose fish, which are Also includes the African elephant nose fish, which are bottom feeders and that use weak electric signals to bottom feeders and that use weak electric signals to communicate with each othercommunicate with each other

Arawanahttp://media-2.web.britannica.com/eb-media/28/117528-004-6B4BBA33.jpg

Arapaimahttp://www.petfishtalk.com/rss_feeds/images/080326_arapaima_1.jpg

http://images.google.com/imgres?imgurl=http://www.bio.davidson.edu/people/midorcas/animalphysiology/websites/2003/Wilson/cfunspics/elephant_nose.jpg&imgrefurl=http://www.bio.davidson.edu/people/midorcas/animalphysiology/websites/2003/Wilson/GalONE.htm&usg=__yE31La06_D121J4Yga5NHWknr5Y=&h=467&w=1458&sz=57&hl=en&start=3&tbnid=xQ3Vx636CuW21M:&tbnh=48&tbnw=150&prev=/images%3Fq%3Delephant%2Bfish%26gbv%3D2%26hl%3Den%26sa%3DG

Elephant nose fish

Teleostei: ElopomorphaTeleostei: Elopomorpha

Elopomorpha: includes tarpons, Elopomorpha: includes tarpons, bonefishes, and eels.bonefishes, and eels.

Specialized leptocephalous [Greek small Specialized leptocephalous [Greek small headed] larvae are a unique feature of the headed] larvae are a unique feature of the group. The larvae spend a long time adrift group. The larvae spend a long time adrift on the ocean being moved by ocean on the ocean being moved by ocean currents.currents.

Bonefishhttp://www.islaculebra.com/puerto-rico/fishing.html

Tarponhttp://www.wildernessaccess.com/images/fishn/Tarpon-FISH-Justin-S-America-Venezuela-Los-Rogos.jpg

EelsEels

Most elopomorphs are eel-like and marine, Most elopomorphs are eel-like and marine, but some tolerate freshwater.but some tolerate freshwater.

The American eel has a very unusual life-The American eel has a very unusual life-cycle. The eels grow to sexual maturity in cycle. The eels grow to sexual maturity in rivers and streams (taking 10 years or rivers and streams (taking 10 years or more) and then migrate downriver into the more) and then migrate downriver into the ocean to breed. (They are ocean to breed. (They are catadramouscatadramous.).)

EelsEels

They swim to the Sargasso Sea (an area of the They swim to the Sargasso Sea (an area of the North Atlantic between the Azores and West North Atlantic between the Azores and West Indies) where they apparently spawn and die, Indies) where they apparently spawn and die, presumably at depth.presumably at depth.

Eggs and larvae float to the surface and drift on Eggs and larvae float to the surface and drift on the currents until they reach the near the coast. the currents until they reach the near the coast. Then they transform into miniature eels and Then they transform into miniature eels and travel up rivers to mature. travel up rivers to mature.

http://www.richardcorfield.com/assets/images/silent_landscape/sargasso.jpg

American Eelhttp://www.peacefulparks.org/800x600/eels/Anguilla-rostrata-2.jpg

Eel larvaehttp://media-2.web.britannica.com/eb-media/17/54217-004-411C3896.gif

EelsEels

European eels also spawn in the Sargasso Sea. European eels also spawn in the Sargasso Sea. Their larvae travel on clockwise currents mainly Their larvae travel on clockwise currents mainly of the Gulf Stream and are distributed to North of the Gulf Stream and are distributed to North Africa, Northern Europe, the Mediterranean and Africa, Northern Europe, the Mediterranean and as far as the Black Sea.as far as the Black Sea.

Because they drift in cooler waters European Because they drift in cooler waters European eels grow more slowly than American eels. eels grow more slowly than American eels. Development is slowed less than growth Development is slowed less than growth however, and as a result European eels have however, and as a result European eels have more vertebrae than American eels.more vertebrae than American eels.

Teleostei: ClupeomorphaTeleostei: Clupeomorpha

Are a commercially very important group of Are a commercially very important group of about 360 species of marine schooling, silvery about 360 species of marine schooling, silvery fishes.fishes.

They include herring, shad, anchovies and They include herring, shad, anchovies and sardines.sardines.

They feed on plankton which they gather using a They feed on plankton which they gather using a specialized mouth and gill-straining apparatus. specialized mouth and gill-straining apparatus.

Herringhttp://pond.dnr.cornell.edu/nyfish/clupeidae/blueback_herring.jpg

EuteleosteiEuteleostei The next major division of the teleosts contains The next major division of the teleosts contains

about 10,000 species.about 10,000 species.

There are four major groups of the EuteleosteiThere are four major groups of the Euteleostei Ostariophysi: carp, catfish, piranhas: about 7,900 Ostariophysi: carp, catfish, piranhas: about 7,900

speciesspecies Salmoniforms: trout, salmon and relatives: about 366 Salmoniforms: trout, salmon and relatives: about 366

speciesspecies Paracanthopterygii: cod and anglerfishes about 1,300 Paracanthopterygii: cod and anglerfishes about 1,300

species.species. ““Stem Neoteleosts” not a monophyletic group, but Stem Neoteleosts” not a monophyletic group, but

includes just over 900 species of lanternfishes and includes just over 900 species of lanternfishes and relatives.relatives.

Euteleostei: OstariophysiEuteleostei: Ostariophysi

Ostariophysi (from Greek for bone and Ostariophysi (from Greek for bone and bladder).bladder).

Represent about 30% of all living fishes, Represent about 30% of all living fishes, about 6500 species. about 6500 species.

Display very diverse traits, but many have Display very diverse traits, but many have protrusible jaws and pharyngeal teeth act protrusible jaws and pharyngeal teeth act as second jaws.as second jaws.


The group possesses two unique derived The group possesses two unique derived features: alarm substances in the skin and the features: alarm substances in the skin and the Weberian apparatus.Weberian apparatus.

When the skin is damaged, pheromones are When the skin is damaged, pheromones are released into the water and these stimulate a released into the water and these stimulate a fright reaction in other members of the species fright reaction in other members of the species and other ostariophysians. In response, they and other ostariophysians. In response, they may quickly seek cover or school together.may quickly seek cover or school together.

Weberian ApparatusWeberian Apparatus

Weberian apparatus: The name ostariophysian Weberian apparatus: The name ostariophysian (Greek bone and bladder) refers to a series of (Greek bone and bladder) refers to a series of small bones that connect the swim bladder with small bones that connect the swim bladder with the inner ear.the inner ear.

The Weberian apparatus greatly enhances The Weberian apparatus greatly enhances hearing in these fish and as a result they are hearing in these fish and as a result they are more sensitive to sounds and can hear a wider more sensitive to sounds and can hear a wider range of sounds than other fishes.range of sounds than other fishes.

Weberian apparatusWeberian apparatus When sound waves strike the swimbladder it When sound waves strike the swimbladder it

vibrates. vibrates.

A bone (the tripus) in contact with the swim A bone (the tripus) in contact with the swim bladder then conducts this vibration via bladder then conducts this vibration via ligaments to two other bones, the second of ligaments to two other bones, the second of which moves and compresses a section of the which moves and compresses a section of the inner ear against a fourth bone.inner ear against a fourth bone.

This fourth bone (the claustrum) then stimulates This fourth bone (the claustrum) then stimulates the auditory region of the inner ear. the auditory region of the inner ear.

Weberian apparatus:http://www.aqua.org.il/pic/Articles/CatFish/12.JPG


The Euteleostei: Ostariophysi includes The Euteleostei: Ostariophysi includes piranhas, tetras, carp and minnows, and piranhas, tetras, carp and minnows, and catfishes.catfishes.

Piranhahttp://blogs.westword.com/latestword/piranha.jpg

Carphttp://www.naturephoto-cz.com/photos/others/carp-20524.jpg

Euteleostei: SalmoniformsEuteleostei: Salmoniforms

The group includes the esocid and salmonid The group includes the esocid and salmonid fishes. fishes.

The salmonids include salmon and trout, which The salmonids include salmon and trout, which include many commercially important species.include many commercially important species.

Many species of salmon are Many species of salmon are anadromousanadromous and and spend their adult lives at sea, but return to breed spend their adult lives at sea, but return to breed in freshwater.in freshwater.


Trout are close relatives of salmon, but Trout are close relatives of salmon, but usually live their entire lives in freshwater.usually live their entire lives in freshwater.

Salmon and trout are important Salmon and trout are important commercial and recreational species. commercial and recreational species.

Coho Salmonhttp://bullsheet.files.wordpress.com/2008/10/coho-salmon.jpg

Rainbow Trout:http://animals.nationalgeographic.com/staticfiles/NGS/Shared/StaticFiles/animals/images/primary/rainbow-trout.jpg


The esocids are relatives of the salmonids and The esocids are relatives of the salmonids and among the most primitive of euteleosteans.among the most primitive of euteleosteans.

They include pike, muskellunge, pickerels and They include pike, muskellunge, pickerels and relatives. relatives.

These fish (which superficially resemble gars) These fish (which superficially resemble gars) are voracious stealth-hunting predators and are voracious stealth-hunting predators and important freshwater game fish.important freshwater game fish.

Northern Pikehttp://www.naturephoto-cz.com/photos/others/northern-pike-20529.jpg

Muskellungehttp://www.rudybenner.com/Cochrane%20District%20Scuba%20Divers_files/Muskellunge.jpg

Euteleostei: ParacanthopterygiiEuteleostei: Paracanthopterygii

Includes about 1,340 species of cod, Includes about 1,340 species of cod, toadfish and anglerfish.toadfish and anglerfish.

Cod and their relatives (including pollock Cod and their relatives (including pollock and haddock) are cold water marine fishes and haddock) are cold water marine fishes and the basis of some of the most and the basis of some of the most historically important marine fisheries. historically important marine fisheries.

Atlantic Cod:http://www.codgen.olsvik.info/Images/Cod7.jpg

AnglerfishesAnglerfishes

Anglerfishes are named for their method of foraging Anglerfishes are named for their method of foraging which involves using a lure to attract fish close to them.which involves using a lure to attract fish close to them.

The lure is a modified spine of the anterior dorsal fin and The lure is a modified spine of the anterior dorsal fin and can be wiggled like a prey item. can be wiggled like a prey item.

In deep sea anglerfish the lure contains bioluminescent In deep sea anglerfish the lure contains bioluminescent bacteria that help attract prey from a distance.bacteria that help attract prey from a distance.

Some bottom-dwelling anglerfish depend on camouflage Some bottom-dwelling anglerfish depend on camouflage and these fish have arm-like pectoral fins that they use and these fish have arm-like pectoral fins that they use to move long the bottom.to move long the bottom.

Anglerfishhttp://scribalterror.blogs.com/scribal_terror/images/2007/06/17/angler_fish.jpg

Black devil Anglerfishhttp://oceanexplorer.noaa.gov/explorations/04deepscope/background/deeplight/media/fig3b_600.jpg

Euteleostei: “Stem Neoteleosts”Euteleostei: “Stem Neoteleosts”

About 916 species of lanternfishes and About 916 species of lanternfishes and their relatives.their relatives.

http://people.whitman.edu/~yancey/lanternventral.jpg

Lantern Fish photophores

Barnard's lanternfish, Symbolophorus barnardi http://www.austmus.gov.au/fishes/faq/images/sbarnardi2.jpg

LanternfishLanternfish The lanternfish is a common resident of the The lanternfish is a common resident of the

upper portions of the deep-sea. It has a series upper portions of the deep-sea. It has a series of light-producing organs along its body, of light-producing organs along its body, especially the belly.especially the belly.

The photophores can vary their intensity and the The photophores can vary their intensity and the fish can tailor the illumination to break up its fish can tailor the illumination to break up its shadow and make it less visible to predators.shadow and make it less visible to predators.

The photophores also appear to be used to The photophores also appear to be used to attract mates.attract mates.

AcanthopterygiiAcanthopterygii

Includes two major groups:Includes two major groups: Atherinomorpha: More than 1,600 species of silversides, Atherinomorpha: More than 1,600 species of silversides,

killifishes, grunions, flying fish and relatives.killifishes, grunions, flying fish and relatives.

These are mostly small silvery fish that are surface These are mostly small silvery fish that are surface feeders.feeders.

There are about 50 species of flying fish (mostly tropical) There are about 50 species of flying fish (mostly tropical) that are members of the Atherinomorpha and they use that are members of the Atherinomorpha and they use their enlarged pectoral fins to glide 50 to 400m their enlarged pectoral fins to glide 50 to 400m (depending on updrafts from waves) to escape (depending on updrafts from waves) to escape predators.predators.

Silversideshttp://www.aboututila.com/Photos/AdamLaverty/Fish-Silversides.JPG

Flying fishhttp://blogs.dispatch.co.za/dispatchnow/files/2008/01/flying-fish.jpg

http://myanimalblog.files.wordpress.com/2008/02/flyingfish.jpg

AcanthopterygiiAcanthopterygii

The second major group is the Perciformes: more than The second major group is the Perciformes: more than 13,000 species of perch and their relatives. 13,000 species of perch and their relatives.

Range in size from 7mm to 5m long. A paraphyletic Range in size from 7mm to 5m long. A paraphyletic group there is no set of derived traits that groups them group there is no set of derived traits that groups them all together, but the they usually have dorsal and anal all together, but the they usually have dorsal and anal fins with anterior spiny portions, whereas the posterior fins with anterior spiny portions, whereas the posterior spines are usually soft rayed. The two portions may be spines are usually soft rayed. The two portions may be partially or completely separated.partially or completely separated.

Snook, sea bass, sunfish, perch, darter, snapper, Snook, sea bass, sunfish, perch, darter, snapper, cichlids, barracuda, tuna, most coral reef fish.cichlids, barracuda, tuna, most coral reef fish.

European Perchhttp://www.strikeit.net/USERIMAGES/PERCH.JPG

Snookhttp://www.floridaadventuring.com/images/snorkeling-school-of-snook.jpg

Black Seabasshttp://shiftingbaselines.org/blog/images/Black%20Sea%20Bass2.jpg

Barracudahttp://www.bubblevision.com/albums/richelieu-rock/images/giant-barracuda.jpg

http://www.practicalfishkeeping.co.uk/pfk/images/cc_barracuda_national_park_service.jpg

SpeciaIizations of the teleostsSpeciaIizations of the teleosts

A major development in the teleosts is the A major development in the teleosts is the conversion of jaws from simple devices for conversion of jaws from simple devices for grasping to sophisticated suction devices.grasping to sophisticated suction devices.

An approaching fish can push prey away, An approaching fish can push prey away, but a rapid expansion of the orobranchial but a rapid expansion of the orobranchial cavity creates a flow of water into the cavity creates a flow of water into the fishes mouth.fishes mouth.

Protrusible jawsProtrusible jaws

Teleosts are characterized by having great Teleosts are characterized by having great mobility in the skeletal elements of the mobility in the skeletal elements of the mouth. This allows the grasping portion of mouth. This allows the grasping portion of the jaws to be quickly extended forward.the jaws to be quickly extended forward.

Jaw protrusion is achieved by levering Jaw protrusion is achieved by levering forward the premaxilla from behind. forward the premaxilla from behind.

The premaxilla is attached with ligaments The premaxilla is attached with ligaments that allow the bone to slide forward on top that allow the bone to slide forward on top of the skull.of the skull.

Protrusible JawsProtrusible Jaws

Based on anatomical comparisons of their Based on anatomical comparisons of their structure in different groups it is clear that structure in different groups it is clear that protrusible jaws have evolved independently protrusible jaws have evolved independently multiple in different teleost clades.multiple in different teleost clades.

Jaw protrusion is widespread among the Jaw protrusion is widespread among the perciform fishes, but also occurs in silversides, perciform fishes, but also occurs in silversides, cods and anglerfishes, and in minnows.cods and anglerfishes, and in minnows.

Pharyngeal JawsPharyngeal Jaws

Mobile and often powerful pharyngeal jaws Mobile and often powerful pharyngeal jaws have evolved several times in have evolved several times in actinopterygians.actinopterygians.

Ancestral ray finned fishes possessed Ancestral ray finned fishes possessed many dermal tooth plates within the many dermal tooth plates within the pharynx. Some toothplates over time pharynx. Some toothplates over time became fused together and to parts of became fused together and to parts of some gill arches. some gill arches.

Pharyngeal jawsPharyngeal jaws

The earliest pharyngeal jaws were not very The earliest pharyngeal jaws were not very mobile, but could be used to hold prey mobile, but could be used to hold prey before swallowing. Today a variety of before swallowing. Today a variety of pharyngeal jaws occur in different groups. pharyngeal jaws occur in different groups.

For example, in minnows the primary jaws For example, in minnows the primary jaws lack teeth but the pharyngeal jaws are lack teeth but the pharyngeal jaws are enlarged and close against a horny pad on enlarged and close against a horny pad on the base of the skull. They are used to grind the base of the skull. They are used to grind plant material.plant material.


In many groups the upper and lower In many groups the upper and lower pharyngeal jaws can move independently pharyngeal jaws can move independently of each other. of each other.

For example, in some moray eels the For example, in some moray eels the pharyngeal jaws can be extended from the pharyngeal jaws can be extended from the throat into the oral cavity to grasp prey and throat into the oral cavity to grasp prey and pull it into the throat and esophagus.pull it into the throat and esophagus.

These X-rays show the normal position of the pharyngeal jaws (upper), and how they can move forward into the mouth to seize food (lower). (Credit: Rita Mehta, Section of Evolution and Ecology and Candi Stafford, School of Veterinary Medicine, UC Davis.) Legend pasted from http://www.sciencedaily.com/releases/2007/09/070905134523.htm

Moray Eel Pharyngeal jawshttp://en.wikipedia.org/wiki/File:Pharyngeal_jaws_of_moray_eels.svg


The cichlids of Lake Victoria have diversified The cichlids of Lake Victoria have diversified enormously into about 500 species in a period of enormously into about 500 species in a period of only about 14,000 years. only about 14,000 years.

The possession of pharyngeal jaws which can The possession of pharyngeal jaws which can process food has allowed the outer jaws to be process food has allowed the outer jaws to be greatly modified to consume a wide variety of greatly modified to consume a wide variety of prey. Foods consumed include, other fish, prey. Foods consumed include, other fish, plankton, algae, fish scales, bivalves, and plankton, algae, fish scales, bivalves, and diatoms.diatoms.

Lobe-finned fishes: Class Lobe-finned fishes: Class SarcoptrygiiSarcoptrygii

Primitive Sarcoptrygians were abundant in Primitive Sarcoptrygians were abundant in the Devonian, but have since declined to a the Devonian, but have since declined to a handful of species.handful of species.

Unlike in the actinopterygians (where the Unlike in the actinopterygians (where the rays fan out from the base of the fin) the rays fan out from the base of the fin) the rays of the paired fins in Sarcopterygians rays of the paired fins in Sarcopterygians extend from a central shaft of bones to extend from a central shaft of bones to support the fin web.support the fin web.

Fin structurehttp://people.eku.edu/ritchisong/RITCHISO//fins2.gif


Primitive Sarcopterygians were 20-70 cm Primitive Sarcopterygians were 20-70 cm long and cylindrical.long and cylindrical.

They possessed two dorsal fins, paired They possessed two dorsal fins, paired pelvic and pectoral fins that were fleshy, pelvic and pectoral fins that were fleshy, scaled and possessed a bony central axis. scaled and possessed a bony central axis. The heterocercal caudal fin had a The heterocercal caudal fin had a epichordal lobe.epichordal lobe.

Fossil Sarcopterygianhttp://www.pc.gc.ca/progs/spm-whs/images/miguasha/mig6b.jpg

http://animals.nationalgeographic.com/staticfiles/NGS/Shared/StaticFiles/animals/images/1024/coelacanth-swimming.jpg


Sarcopterygian fishes also had massive Sarcopterygian fishes also had massive jaw muscles in comparison to those of jaw muscles in comparison to those of actinopterygians.actinopterygians.

In addition, early sarcopterygians were In addition, early sarcopterygians were covered with a dentine-like material called covered with a dentine-like material called cosmine.cosmine.


Today the sarcopterygians are a very Today the sarcopterygians are a very small group that includes only six species small group that includes only six species of lungfishes (Dipnoi) and two species of of lungfishes (Dipnoi) and two species of coelacanths (Actinistia).coelacanths (Actinistia).

However, all of the tetrapods (four-legged However, all of the tetrapods (four-legged vertebrates) are descended from an vertebrates) are descended from an extinct group of sarcopterygian fishes extinct group of sarcopterygian fishes known as the rhipidistians.known as the rhipidistians.

LungfishesLungfishes

There are six species of lungfishes: one There are six species of lungfishes: one South American, one Australian and four South American, one Australian and four African species.African species.

As their name suggests, these fish, as all As their name suggests, these fish, as all sarcopterygians do, possess alveolar sarcopterygians do, possess alveolar lungs and can breathe air.lungs and can breathe air.


Extant Dipnoi have lost the articulating toothed Extant Dipnoi have lost the articulating toothed premaxillary and maxillary bones of the other premaxillary and maxillary bones of the other Osteichthyes.Osteichthyes.

They have crushing dental plates with fan-They have crushing dental plates with fan-shaped ridges and teeth scattered over the shaped ridges and teeth scattered over the palate. In addition, strong muscles attach the palate. In addition, strong muscles attach the lower jaw to the chondrocranium. Lungfishes lower jaw to the chondrocranium. Lungfishes are thus specialized to feed on hard foods such are thus specialized to feed on hard foods such as crustaceans and molluscs.as crustaceans and molluscs.


The dorsal, caudal and anal fins have fused into The dorsal, caudal and anal fins have fused into a single continuous fin that extends around the a single continuous fin that extends around the entire rear third of the body.entire rear third of the body.

The change in body form of the lungfishes may The change in body form of the lungfishes may be an example of paedomorphosis.be an example of paedomorphosis.

They were initially considered to be salamanders They were initially considered to be salamanders when first described.when first described.


The Australian lungfish can gulp air and survive The Australian lungfish can gulp air and survive being in oxygen poor water, but cannot live out being in oxygen poor water, but cannot live out of water. of water.

In contrast, the South American and African In contrast, the South American and African species can survive out of water for long periods species can survive out of water for long periods of time. of time.

The African species live in seasonal steams and The African species live in seasonal steams and ponds that dry out, but the lungfish survives by ponds that dry out, but the lungfish survives by burrowing into the mud and forming a cocoon in burrowing into the mud and forming a cocoon in which it survives until the water returns.which it survives until the water returns.

African lungfishhttp://www.amtra.de/images/Lungenfisch415.jpg

South American Lungfishhttp://www.ucmp.berkeley.edu/vertebrates/sarco/lungfish1.jpg

Australian Lungfishhttp://www.nhm.ac.uk/about-us/news/2007/october/images/Australian%20lungfish%20copyright%20Jean%20Joss-370_12548_1.jpg

Figure 24.22

The discovery of living coelacanthsThe discovery of living coelacanths

Coelacanths were believed to have been extinct Coelacanths were believed to have been extinct for perhaps 50 million years (there are fossils for perhaps 50 million years (there are fossils identical in appearance that are 70 million years identical in appearance that are 70 million years old) when one was caught by a South African old) when one was caught by a South African fishing boat in 1938.fishing boat in 1938.

The curator of a small museum, M. Courtney-The curator of a small museum, M. Courtney-Latimer, recognized the fish was unusual and Latimer, recognized the fish was unusual and she brought it to the attention of the icthyologist she brought it to the attention of the icthyologist J.L.B. Smith who after some delay in arriving J.L.B. Smith who after some delay in arriving identified the fish. identified the fish.

The discovery of living coelacanthsThe discovery of living coelacanths

Unfortunately, the delay in arriving meant the fish had Unfortunately, the delay in arriving meant the fish had badly decomposed and many important structures had badly decomposed and many important structures had been lost.been lost.

Smith named the fish (Smith named the fish (LatimeriaLatimeria) in honor of Courtney-) in honor of Courtney-Latimer and then embarked on a 14-year quest to find Latimer and then embarked on a 14-year quest to find another coelacanth. another coelacanth.

But it wasn’t until 1952 that a second was caught off the But it wasn’t until 1952 that a second was caught off the Comoro Islands, north of Madagascar, which is where Comoro Islands, north of Madagascar, which is where the fish occur naturally (the 1938 fish apparently had the fish occur naturally (the 1938 fish apparently had drifted far from its normal range). The story is told in drifted far from its normal range). The story is told in Smith’s book “The search beneath the sea.”Smith’s book “The search beneath the sea.”

Images from the rediscovery of the Coelacanth off the Comoros 1952.

CoelacanthsCoelacanths

In 1998 another population of In 1998 another population of LatimeriaLatimeria [but a [but a different species] was discovered off Indonesia different species] was discovered off Indonesia (10,000km east of the Comoros).(10,000km east of the Comoros).

Coelacanths are large fish up to about 5 feet Coelacanths are large fish up to about 5 feet long, blue-grey in color with white spots.long, blue-grey in color with white spots.

They live in deep (70-400m) cold water and are They live in deep (70-400m) cold water and are predators feeding mainly on lanternfish.predators feeding mainly on lanternfish.

16.20

Figure 24.23


Coelacanths are readily identified from their fins. Coelacanths are readily identified from their fins. The caudal fin has a small median lobe.The caudal fin has a small median lobe. Each of the paired fins is very mobile and has a long Each of the paired fins is very mobile and has a long

fleshy basal lobe.fleshy basal lobe. The anterior dorsal fin’s fleshy lobe is reduced and it The anterior dorsal fin’s fleshy lobe is reduced and it

possesses long protective hollow spines (coelacanth possesses long protective hollow spines (coelacanth means “hollow spine”).means “hollow spine”).

When they swim coelacanths move their pelvic and When they swim coelacanths move their pelvic and pectoral fins in the same pattern that tetrapods walk.pectoral fins in the same pattern that tetrapods walk.


Because coelacanths possess an unusual suite Because coelacanths possess an unusual suite of characters including fat-filled lungs, a high of characters including fat-filled lungs, a high level of urea in the blood, a liquid filled level of urea in the blood, a liquid filled notochord, lobed fins, ventral kidneys and a notochord, lobed fins, ventral kidneys and a reduced brain there has been debate about their reduced brain there has been debate about their phylogenetic affinities.phylogenetic affinities.

The consensus today is that coelacanths are a The consensus today is that coelacanths are a sister group to the Rhipidistia which gave rise to sister group to the Rhipidistia which gave rise to the lungfish and tetrapods.the lungfish and tetrapods.

We will discuss the origins of the tetrapods We will discuss the origins of the tetrapods shortly.shortly.

Global fisheries and conservationGlobal fisheries and conservation

Before moving on from fishes to the Before moving on from fishes to the tetrapods, I want to devote some time to tetrapods, I want to devote some time to fishing.fishing.

It is a sad fact that global fish stocks have It is a sad fact that global fish stocks have been enormously depleted and in most been enormously depleted and in most places fish populations are a pale shadow places fish populations are a pale shadow of their former abundance.of their former abundance.


For example: Captain John Smith describing For example: Captain John Smith describing tributaries of the Chesapeake in 1608 “… in tributaries of the Chesapeake in 1608 “… in diverse places that abundance of fish lying so diverse places that abundance of fish lying so thicke with their heads above the water, as for thicke with their heads above the water, as for want of nets we attempted to catch them with a want of nets we attempted to catch them with a frying pan, but we found it a bad instrument to frying pan, but we found it a bad instrument to catch fish with. Neither better fish more plenty catch fish with. Neither better fish more plenty or variety had any of us ever seene, in any place or variety had any of us ever seene, in any place swimming in the water than in the Bay of the swimming in the water than in the Bay of the Chesapeack, but there not to be caught with Chesapeack, but there not to be caught with frying pans.”frying pans.”


Captain John Smith again: Having Captain John Smith again: Having grounded on an oyster bed in the Potomac grounded on an oyster bed in the Potomac as the tide was going out “…we spied as the tide was going out “…we spied many fishes lurking amongst the weeds on many fishes lurking amongst the weeds on the sands, our captaine sporting himself to the sands, our captaine sporting himself to catch them by nailing them to the ground catch them by nailing them to the ground with his sword, set us all a fishing in that with his sword, set us all a fishing in that manner, by this devise, we tooke more in manner, by this devise, we tooke more in an houre than we all could eat.”an houre than we all could eat.”


Clearly a different level of fish abundance Clearly a different level of fish abundance than we encounter today. than we encounter today.

Similarly abundant numbers of fish were Similarly abundant numbers of fish were described in the waters off New England described in the waters off New England and eastern Canada.and eastern Canada.

The Grand Banks fisheryThe Grand Banks fishery

John Cabot voyaged to Newfoundland in John Cabot voyaged to Newfoundland in 1497. The Milanese ambassador to 1497. The Milanese ambassador to London reported what he had heard from London reported what he had heard from Cabot about the fishing there: “they assert Cabot about the fishing there: “they assert that the sea there is swarming with fish, that the sea there is swarming with fish, which can be taken not only with the net, which can be taken not only with the net, but in baskets let down with a stone, so but in baskets let down with a stone, so that it sinks in the water. I have heard this that it sinks in the water. I have heard this Messer Cabot state so much.”Messer Cabot state so much.”

The Grand Banks fisheryThe Grand Banks fishery Two centuries later Pierre de Charlevoix in 1719 Two centuries later Pierre de Charlevoix in 1719

described the Grand Banks of Newfoundland described the Grand Banks of Newfoundland “What is called the great bank of Newfoundland “What is called the great bank of Newfoundland … you find on it a prodigious quantity of shell-… you find on it a prodigious quantity of shell-fish, with several other sorts of fishes of all sizes, fish, with several other sorts of fishes of all sizes, most part of which serve for the common most part of which serve for the common nourishment of the cod, the number of which nourishment of the cod, the number of which seems to equal that of the grains of sand which seems to equal that of the grains of sand which cover this bank. For more than two centuries cover this bank. For more than two centuries since, there have been loaded with them two to since, there have been loaded with them two to three hundred ships annually, notwithstanding three hundred ships annually, notwithstanding the diminution is not perceivable.”the diminution is not perceivable.”

The Grand Banks fisheryThe Grand Banks fishery The rich fishing grounds off the northeastern U.S. and The rich fishing grounds off the northeastern U.S. and

eastern Canada result from a combination of factors.eastern Canada result from a combination of factors.

The various banks (the Grand Banks, George’s Bank, The various banks (the Grand Banks, George’s Bank, Brown’s Bank and others) are deposits of moraine Brown’s Bank and others) are deposits of moraine deposited by glaciers. deposited by glaciers.


The water above them is relatively shallow (60-The water above them is relatively shallow (60-300 feet in most places) and they occur at the 300 feet in most places) and they occur at the confluence of the cold nutrient rich northern confluence of the cold nutrient rich northern Labrador current and the warm southern Gulf Labrador current and the warm southern Gulf Stream.Stream.

The mixing of these currents combines warmth The mixing of these currents combines warmth and nutrients to produce massive blooms of and nutrients to produce massive blooms of plankton that supported huge schools of plankton that supported huge schools of mackerel and herring that in turn supported cod mackerel and herring that in turn supported cod and other predators.and other predators.

The Grand Bankshttp://www.immersionpresents.org/photos/albums/userpics/10179/Grand_Banks_Map.jpg

George’s Bank and Brown’s Bankhttp://www.nefsc.noaa.gov/history/timeline/images/georges.jpg


In 1992 the Canadian Government placed a two In 1992 the Canadian Government placed a two year moratorium on cod fishing, which was year moratorium on cod fishing, which was extended indefinitely and remains in place today. extended indefinitely and remains in place today. In 2003 the two main populations of Atlantic cod In 2003 the two main populations of Atlantic cod were added to Canada’s endangered species were added to Canada’s endangered species list.list.

In U.S. waters cod populations have similarly In U.S. waters cod populations have similarly plummeted.plummeted.

What happened? Industrial fishing happened.What happened? Industrial fishing happened.


Up until the early 20Up until the early 20thth century, cod-fishing had century, cod-fishing had been almost exclusively by schooners using been almost exclusively by schooners using hand lines but then steam trawlers were hand lines but then steam trawlers were introduced to North America. With their introduced to North America. With their greater greater fishing powerfishing power the steam trawlers soon replaced the steam trawlers soon replaced the schooners and had become common by the the schooners and had become common by the 1920’s. 1920’s.

Around the same time fast-freezing technology Around the same time fast-freezing technology was developed and the frozen fillet entered the was developed and the frozen fillet entered the marketplace. marketplace.

http://www.pugetsoundmagazine.com/articles/img001/10024/lituya1FVOA.jpg

Fishing schooner Olympic about 1911.

Norwegian Cod schooner 1930http://pro.corbis.com/images/US002037.jpg?size=67&uid=%7B15ED58FC-EBD7-4EDF-8067-DA989C5D9ECD%7D

Steam Trawler Bellerophon http://www.maritimelowestoft.co.uk/images/crownies_lowestoft/bellerophon_large.jpg

The Grand Banks fisheryThe Grand Banks fishery One of the first fish to be targeted by ships using One of the first fish to be targeted by ships using

the the new technologynew technology was haddock. was haddock.

Haddock freezes well (but salts poorly and Haddock freezes well (but salts poorly and previously had been thrown away by fishermen). previously had been thrown away by fishermen).

Huge spawning aggregations were discovered on Huge spawning aggregations were discovered on the Georges Bank and heavily fished for.the Georges Bank and heavily fished for.

Catches soared through the 1920’s peaking at Catches soared through the 1920’s peaking at 120,000 tonnes in 1929. 120,000 tonnes in 1929.


In 1930 an estimated 37 million haddock were In 1930 an estimated 37 million haddock were landed in Boston. However, even more were landed in Boston. However, even more were discarded because small mesh nets discarded because small mesh nets caught fish caught fish indiscriminatelyindiscriminately and more than two juvenile and more than two juvenile haddock were discarded for each adult landed.haddock were discarded for each adult landed.

Not surprisingly haddock numbers crashed Not surprisingly haddock numbers crashed falling to 28,000 tonnes by 1934. Landings of falling to 28,000 tonnes by 1934. Landings of about 50,000 tonnes per year were sustained about 50,000 tonnes per year were sustained into the 1960’s but only because the fishermen into the 1960’s but only because the fishermen began fishing in new watersbegan fishing in new waters. .


In the 1960’s fishing pressure increased In the 1960’s fishing pressure increased immensely as distant-water fishing fleets immensely as distant-water fishing fleets from Europe moved in to fish (national from Europe moved in to fish (national fishing limits were only 3 miles).fishing limits were only 3 miles).

Fleets from Britain, Spain, Portugal, Fleets from Britain, Spain, Portugal, Romania, France, West Germany, Poland, Romania, France, West Germany, Poland, East Germany and Russia crowded into East Germany and Russia crowded into the fishing grounds. the fishing grounds.


The European fishing fleets consisted of groups The European fishing fleets consisted of groups of factory trawlers supplying mother ships that of factory trawlers supplying mother ships that processed the catch and these had immense processed the catch and these had immense fishing and processing capacity (thousands of fishing and processing capacity (thousands of tons a day) much greater than local fleets.tons a day) much greater than local fleets.

In an hour a single factory trawler could catch In an hour a single factory trawler could catch 200 tons of fish, twice as much as a 16th century 200 tons of fish, twice as much as a 16th century ship could have caught in an whole season’s ship could have caught in an whole season’s fishing.fishing.


Onboard the mother ships, fish was machine-Onboard the mother ships, fish was machine-filleted and frozen or turned into fishmeal. filleted and frozen or turned into fishmeal. These ships could fish in any kind of weather These ships could fish in any kind of weather and stay at sea for months on end. and stay at sea for months on end.

In 1965 the Soviet Union had 106 factory In 1965 the Soviet Union had 106 factory trawlers and 425 smaller trawlers supplying 30 trawlers and 425 smaller trawlers supplying 30 mother ships and together these took 872,000 mother ships and together these took 872,000 tonnes of fish. tonnes of fish.

Russian factory trawlerhttp://www.greenpeace.org/raw/image_full/international/photosvideos/photos/russian-factory-trawler-fishin.jpg


Fishing fleets were able to work Fishing fleets were able to work cooperatively to exhaust aggregations of cooperatively to exhaust aggregations of fish. When a concentration of fish was fish. When a concentration of fish was found (using the most sophisticated found (using the most sophisticated available search equipment) the trawlers available search equipment) the trawlers would aggregate to fish it into oblivion would aggregate to fish it into oblivion before dispersing again to seek new before dispersing again to seek new schools.schools.


By 1974 more than 1,000 European By 1974 more than 1,000 European vessels were fishing the banks. Their vessels were fishing the banks. Their catch was more than 2 million tonnes, catch was more than 2 million tonnes, which was 3x the Canadian catch and 10x which was 3x the Canadian catch and 10x the New England catch.the New England catch.

Everything was taken juvenile or adult, Everything was taken juvenile or adult, spawning or not regardless of the future spawning or not regardless of the future impact on stocks.impact on stocks.


Two Canadian fisheries scientists, Jeffrey Two Canadian fisheries scientists, Jeffrey Hutchings and Ransom Myers, have estimated Hutchings and Ransom Myers, have estimated that about eight million tons of northern cod were that about eight million tons of northern cod were caught between Cabot's arrival in 1497 and caught between Cabot's arrival in 1497 and 1750, over the course of 25 to 40 cod 1750, over the course of 25 to 40 cod generations. generations.

Factory trawlers took the same amount in only Factory trawlers took the same amount in only 15 years, a period less than the lifetime of a 15 years, a period less than the lifetime of a single cod. single cod.


Catches of fish far exceeded sustainable Catches of fish far exceeded sustainable yields and fisheries began to collapse. yields and fisheries began to collapse. The haddock fishery in the Gulf of Maine The haddock fishery in the Gulf of Maine collapsed in the 1970’s.collapsed in the 1970’s.

In 1977 following Iceland’s lead the U.S. In 1977 following Iceland’s lead the U.S. and Canada declared a 200-mile limit and and Canada declared a 200-mile limit and excluded the foreign fishing boats.excluded the foreign fishing boats.


Instead of attempting to hold down fishing Instead of attempting to hold down fishing efforts both countries expanded their efforts both countries expanded their fleets.fleets.

Between 1977 and 1982 the number of Between 1977 and 1982 the number of New England trawlers increased from 825 New England trawlers increased from 825 to more than 1,400 boats. Domestic to more than 1,400 boats. Domestic overfishing replaced foreign overfishing.overfishing replaced foreign overfishing.


By the early 1980’s fishing catches had By the early 1980’s fishing catches had risen to twice the level that was risen to twice the level that was sustainable, but by investing in more sustainable, but by investing in more sophisticated equipment fishermen could sophisticated equipment fishermen could still make a living.still make a living.

However, at this point fishermen were However, at this point fishermen were killing 60-80% of all the cod, haddock and killing 60-80% of all the cod, haddock and flounder in the Gulf of Maine every year.flounder in the Gulf of Maine every year.


In the mid-1980’s U.S. fisheries scientists In the mid-1980’s U.S. fisheries scientists saw the collapse coming and pushed for saw the collapse coming and pushed for major cuts in fish landings, but the fishing major cuts in fish landings, but the fishing industry resisted cuts and it wasn’t until industry resisted cuts and it wasn’t until the mid 1990’s that reductions were the mid 1990’s that reductions were imposed.imposed.


A similar process played out in Canadian waters. A similar process played out in Canadian waters. Canadian fisheries scientists overestimated Canadian fisheries scientists overestimated sustainable yields of cod based on a series of sustainable yields of cod based on a series of bad assumptions. In the 1980’s 5x times as bad assumptions. In the 1980’s 5x times as many cod were being taken as should have many cod were being taken as should have been removed.been removed.

Calls to cut back the fishery were ignored and by Calls to cut back the fishery were ignored and by 1992 the fishery was finished. 1992 the fishery was finished.


Estimates of the size of the original Estimates of the size of the original population suggest that there were about 7 population suggest that there were about 7 million tonnes of cod off the Atlantic coast million tonnes of cod off the Atlantic coast of Canada in 1505. of Canada in 1505.

By 1992 the estimate was 22,000 tonnes By 1992 the estimate was 22,000 tonnes (<1/3 of 1% of the original population.).(<1/3 of 1% of the original population.).

The Grand Banks fisheryThe Grand Banks fishery Cod have not made a comeback and there is Cod have not made a comeback and there is

some debate about why.some debate about why.

However, habitat transformation almost certainly However, habitat transformation almost certainly has played a major role.has played a major role.

Before trawling, the sea bottom on the banks Before trawling, the sea bottom on the banks was not a layer of mud. Rocks outcrops, was not a layer of mud. Rocks outcrops, boulders and stones provided structure, places boulders and stones provided structure, places for young fish to hide and rich communities of for young fish to hide and rich communities of sponges, crabs, mussels, anemones, tube sponges, crabs, mussels, anemones, tube worms and other invertebrates flourished.worms and other invertebrates flourished.


A bottom trawler’s net is held open by large A bottom trawler’s net is held open by large metal doors weighing thousands of pounds and metal doors weighing thousands of pounds and the bottom of the bag is kept on the seabed by a the bottom of the bag is kept on the seabed by a weighted metal cable. Each pass of a net drags weighted metal cable. Each pass of a net drags boulders and rocks, buries and crushes boulders and rocks, buries and crushes invertebrates and leaves behind a virtual invertebrates and leaves behind a virtual moonscape.moonscape.

Bottom trawling is the ecological equivalent of Bottom trawling is the ecological equivalent of clear-cutting, but carried out on a much more clear-cutting, but carried out on a much more massive scale and out of view. massive scale and out of view.

http://newsimg.bbc.co.uk/media/images/40874000/gif/_40874232_bottom_trawling_416.gif

http://coralnotesfromthefield.blogspot.com/2007_05_01_archive.html

Sea bottom habitat in Canada (left) and Australia (right) before trawling (above) and after (below).


After years of bottom trawling the sea bed After years of bottom trawling the sea bed has been converted from a rich diverse has been converted from a rich diverse ecosystem to a sterile one. ecosystem to a sterile one.

Unfortunately, the tragedy of the cod Unfortunately, the tragedy of the cod fishery is just one example of failed fishery is just one example of failed fisheries and the pattern has been fisheries and the pattern has been repeated worldwide.repeated worldwide.

Documents

Living fishes The living fishes (not a monophyletic group) include: the jawless fishes (e.g. lampeys), the jawless fishes (e.g. lampeys), cartilaginous